BORING INFO
Further to my instructions on how to do a DIY timing-cover oil seal conversion on pre-unit Triumphs, Steve Kedian is keen to try it, but got in touch to ask where he could get a cutting tool thin enough to bore out the circlip groove inside the hole. The answer is to make your own, Steve. You need a piece of tough steel bar that will fit in the chuck of your boring head; a useful source of material is an old wheel spindle, that should be plenty strong enough. This is the tool holder.
The actual cutting tool can be made from high-speed steel round bar; you could also use hardened and tempered silver steel, but I always save any broken centre drills to recycle for this purpose – a HSS twist drill bit shank would do too. Grind the nose of the tool to whatever size and profile you need, then cross-drill the holder to suit the diameter of the tool and drill and tap a hole in the end to secure it with a grub screw.
Obviously you should only take light cuts – there’s a danger that the grub screw could slip and spoil the job if too much force is used, but I’ve never had a problem. One thing I did suggest to Dave, though, is that it might be wise to get a block of aluminium to practice on before starting on the actual engine casing.